Last updated: 2026-10-31
Wire Run is a free DC wire size and voltage drop calculator, with charts and worked examples. These terms cover using the calculator and joining the email list. Nothing on this site is for sale, and no payment details are collected anywhere on it.
The calculator runs in your browser. It does arithmetic on the numbers you enter, using published resistance figures for copper conductors and the ampacity figures named on each page. It is free to use, and you do not need an account.
It is not an engineering service and it does not certify an installation. A wire size that passes here can still be wrong for your installation: ambient temperature, bundling, conduit, insulation type, engine rooms, the equipment maker's instructions, and the standards and codes that apply where you are can all require something different. Check your work against those, or have a qualified person check it, before you rely on it. You use the results at your own risk.
We try to keep the figures and the arithmetic right. If you find a mistake, tell us through the contact form at /contact.html and we will fix it.
If you enter your email address, you are asking us to email you the printable wire chart when it is ready and to tell you when we add a new calculator. That is the whole agreement.
Write to us via the contact form at /contact.html and ask, and we will delete your address. You do not need a reason. See the privacy policy for the detail.
Nothing here limits liability that cannot legally be limited, including for fraud, or for death or personal injury caused by negligence. Otherwise, because this site is free and provides calculations rather than advice, we are not liable for loss or damage arising from a wiring decision made using it.
If we change these terms materially while you are on the list, we will tell you by email.